The invention relates to a pneumatic wall structure and a method of making and erecting same. The invention is suitable for worldwide use under extreme climatic conditions and is highly mobile. The wall structure can be used as an add-on to an existing shelter having fixed walls. It is also possible to erect a complete building enclosed on several sides from the pneumatic wall structure of the present invention.
Pneumatic structures are closely associated with the architect Frei Otto. An overview of his work is provided, for instance, in M. Kawaguchi: Der umgekehrte Weg, arcus Architektur und Wissenschaft 10 (1990).
Tubes (rafters) filled with compressed air and optionally secured with braces can also be used as support structures for pneumatic buildings.
The heat transfer coefficients of such pneumatic structures are generally considered as moderate to poor. Furthermore, sun protection and CBR protection require additional covering, which in turn prolongs the erection time. For emergency medical use, which places high demands on mobility, erection time and packing volume, adds substantial additional transport volume and weight. A pneumatic building set up as an operating room or an intensive care unit, for example, must be supplied not only with electricity for the medical equipment, but also with air-conditioning. Accordingly, it is advantageous to decrease the start-up times required for the erection of the buildings themselves, the equipment, as well as the startup time for the energy supply and the air-conditioning.
A decrease in start-up time can be achieved if the energy requirement for the air-conditioning is reduced, i.e., if thermal insulation is improved and the erection and dismantling process is at least partially automated.
The present invention achieves at least these goals by providing a pneumatic wall structure comprising an inner flexible tent sheet, a central flexible tent sheet and an outer flexible tent sheet. The inner, the central and the outer flexible tent sheets are arranged to form a two-layer wall structure comprising (i) an inner layer formed by the inner tent sheet and the central tent sheet and, (ii) an outer layer formed by the central tent sheet and the outer tent sheet. The inner layer is inflatable and provides a main support structure for the wall structure, and the outer layer forms a convection space into which an ambient air is capable of flowing. The inflatable support tubes are arranged between the central tent sheet and the outer tent sheet to provide redundancy to the main support structure and to provide a spacer between the central tent sheet and the outer tent sheet.
While retaining the pneumatic construction principles xe2x80x9cair-supported structurexe2x80x9d and xe2x80x9cinflatable structure (support tube structure)xe2x80x9d (for definitions see M. Kawaguchi loc. cit.), the present invention includes a two-layer wall structure made of 3 tent sheets (inner, outer and central tent sheet). The inner layer, preferably having a pressure of about 300 Pa above atmospheric pressure, forms the main support structure of the wall structure. Advantageously, the delimiting tent sheets (inner and central tent sheet) are connected by flexible ribs for stability, spacing and for suppressing convection currents. Stability is achieved by way of a slight overpressure within the interior due to a fresh air supply of the air conditioning system.
The second outer air layer between the central and outer tent sheet communicates with ambient air through air intake openings and air outlet openings near a floor and in a ridge area (e.g., air intake or air outlet screens). If the outer tent sheet is heated compared to the ambient temperature as a result of solar radiation, a rising convection current starts within the chambers along all the outer walls of the building.
Pressurized support tubes act as spacers while at the same time acting as a secondary, redundant support structure between the central and the outer tent sheets. The support tubes can be inflated individually.
If high solar radiation is expected, it may be advantageous to distinctly limit the heat transfer from the outer tent sheet exposed to the sun (olive green for military applications) to the interior. This may be accomplished by metallizing the central tent sheet on the surface facing the exterior by a suitable metallic coating or by vapor deposition in the wavelength range of the thermal radiation.
With the double air layer construction according to the invention, heat transfer is clearly reduced compared to a single tent sheet arrangement. Even for areas exposed to the sun, the cooling capacity is determined only by the difference between ambient temperature and interior room temperature (and not by the difference between surface temperature and interior room temperature).
A further advantageous embodiment forms the base of a pneumatic building formed with the pneumatic wall structure of the present invention as square as possible and the shape of the building as seen in a vertical cross section as elliptical or curved in some other way, so that along the edge area the interior height is just sufficient and in the center it is no higher than required for an adequate standing height and the mounting of the air distribution unit.
The object of shortening the erection time and reducing the number of required personnel during assembly is achieved since, after manually unrolling the building package, first the inner, load-bearing, segmented air chambers of the inner layer are pressurized by way of a programmably controlled air compressor or similar device as would be appreciated by one of ordinary skill in the art. In the next step, the support tubes (inflated separately) are pressurized to lift the outer tent sheet. The switch of the flow paths is triggered by pressure sensors (or by a pressure gauge in manual operation). Pressure maintenance or an increase in the interior pressures in case of side forces due to high wind speeds is effected in the same way.
Dismantling of the wall structure according to the invention is accelerated by sequentially drawing off the excess pressure.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.